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Chapter 7 - Landforms & Their Evolution

"Geomorphology" - Study of the earth surface

A landform is a feature on the Earth's surface that is part of the terrain. Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms include buttes, canyons, valleys, and basins.



Landforms by Rivers

Erosion
The Erosion results first into Rills then - Gullies then - Valleys

  • Rills - are narrow and shallow channels which are eroded into unprotected soil by hillslope runoff. 
  • Gully - is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys
  • Valley - is a low area between hills, often with a river running through it. Types - 

V-Shape Valley - formed in Mountain region
U-Shape Valley - carved by glaciers


  • Canyon or Gorge - is a deep ravine between pairs of escarpments or cliffs
  • Potholes - are cylindrical holes drilled into the bed of a river that vary in depth & diameter from a few centimetres to several metres. They’re found in the upper course of a river
  • Meanders - are bends in a river that form as a river’s sinuosity increases. The sinuosity of a river is a measurement of how much a river varies from a straight line.
  • Oxbow Lakes - Oxbow lakes are an evolution of meanders that undergo extensive deposition and erosion. Strong erosion takes place on the outside bend of a meander while deposition takes place on the inside bend. As a result, the neck of a meander narrows. Deposition eventually separates the cutoff from the main channel leaving behind an oxbow lake.


Deposition

  • Alluvial fan - is a fan- or cone-shaped deposit of sediment crossed and built up by streams. Mostly formed in Arid & Semi Arid climates
  • Floodplains - Floodplains are large, flat expanses of land that form on either side of a river. The floodplain is the area that a river floods onto when it’s experiencing high discharge. 
  • Natural Levees - are natural embankments produced, ironically, when a river floods. When a river floods, it deposits its load over the flood plain due to a dramatic drop in the river’s velocity as friction increases greatly.
  • Deltas - are depositional landforms found at the mouth of a river where the river meets a body of water with a lower velocity than the river

Term "Delta" is coined by Herodotus (father of Geography)

Landforms by Glaciers

  • Cirque - are Armchair shaped hollow floor formed by sliding snow
  • Tarn - are lakes formed by melted glacier of Cirque
  • Fiord - are narrow inlet with steep sides created by glacial erosion
  • U-Shape Valley - formed by glacial erosion
  • Hanging Valley - formed with the help of tributary
  • Moraine - are materials transported & deposited by glacier
  • Eskers - are Zig Zag hills with sand & gravels
  • Drumlines - are Oval shaped hills


Landforms by Wind

  • Mushroom rock - also called rock pedestal or a pedestal rock, is a naturally occurring rock whose shape resembles a mushroom. Usually found in desert areas, these rocks form over thousands of years when wind erosion 
  • Sand Dunes - is a hill of sand built by wind by accumulation of sand grains shaped into a mound or ridge by the wind under the influence of gravity.
  • Barchan - are crescent-shaped sand dunes
  • Loess - are finer soils in silt form found in desert

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